strange effect: if ... else in C influence a previous statement Post: 302260273

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Top Forums Programming strange effect: if ... else in C influence a previous statement Post 302260273 by cdbug on Thursday 20th of November 2008 04:31:04 AM

11-20-2008

Registered User

strange effect: if ... else in C influence a previous statement

I write a short code in c

it may work well, but when I add an if ... else ... structure, a computation before the structure can not give a correct result

compilation and run can do well, but the result is wrong. Very strange

(1)
y2 = expression; //y2 = 0 always 0 error
.................

add : if(a->is_root) c = m2 - y2;
else f = m2 - y2;

(2)

y2 = expression; //y2 = 0 always 0 error
.................

add : if(a->is_root) c = m2 - y2;
if(!a->is_root) f = m2 - y2;

(3)
y2 = expression; // y2 = normal value; normal
.................

add : //if(a->is_root) c = m2 - y2;
if(!a->is_root) f = m2 - y2;

(4)

y2 = expression; // y2 = normal value; normal
.................

add : if(a->is_root) c = m2 - y2;
//if(!a->is_root) f = m2 - y2;

(5)
y2 = expression; // y2 = normal value; normal

add : //if(a->is_root) c = m2 - y2;
//if(!a->is_root) f = m2 - y2;

Trouble: can not use if... else ... normally

Question: (1) if... else ... can influence a previous statement, why?
(2) How to solve the problem?

Last edited by cdbug; 11-20-2008 at 05:38 AM..

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LEARN ABOUT DEBIAN

ausearch_add_timestamp_item

AUSEARCH_ADD_TIMESTAMP_ITEM(3)					  Linux Audit API				    AUSEARCH_ADD_TIMESTAMP_ITEM(3)

NAME

       ausearch_add_timestamp_item - build up search rule

SYNOPSIS

       #include <auparse.h>

       int ausearch_add_timestamp_item(auparse_state_t *au, const char *op, time_t sec, unsigned milli, ausearch_rule_t how)

DESCRIPTION

       ausearch_add_timestamp_item  adds an event time condition to the current audit search expression. The search conditions can then be used to
       scan logs, files, or buffers for something of interest. The op parameter specifies the desired comparison. Legal op values are <, <=, >=, >
       and  =.	 The left operand of the comparison operator is the timestamp of the examined event, the right operand is specified by the sec and
       milli parameters.

       The how value determines how this search condition will affect the existing search expression if one is already defined. The possible  val-
       ues are:

	      AUSEARCH_RULE_CLEAR
		     Clear the current search expression, if any, and use only this search condition.

	      AUSEARCH_RULE_OR
		     If a search expression E is already configured, replace it by (E || this_search_condition).

	      AUSEARCH_RULE_AND
		     If a search expression E is already configured, replace it by (E && this_search_condition).

RETURN VALUE

       Returns -1 if an error occurs; otherwise, 0 for success.

APPLICATION USAGE

       Use  ausearch_add_item(3)  and ausearch_add_interpreted_item(3) to add conditions that check audit record fields.  Use ausearch_add_expres-
       sion(3) to add complex search expressions using a single function call.

SEE ALSO

       ausearch_add_expression(3),  ausearch_add_item(3),  ausearch_add_interpreted_item(3),  ausearch_add_regex(3),  ausearch_set_stop(3),  ause-
       arch_clear(3), ausearch_next_event(3), ausearch-expression(5).

AUTHOR

       Miloslav Trmac

Red Hat 							     Nov 2007					    AUSEARCH_ADD_TIMESTAMP_ITEM(3)